ON THE SYNCARIDA. 125 
fifth joint thicker than the fourth, thickening towards the distal end, with four spines, the fourth 
spine the largest and as long as the joint is thick ; the sixth about two-thirds as thick as the fifth, 
with two remote spines on the under side and ending in two spines, one of them very large and 
stout (there is possibly a third small spine). In Meek and Worthen’s figures the spines are errone- 
ously drawn on the outer side of four joints; we find that the spines are situated only on the two 
penultimate joints; the terminal claw is not represented by Meek and Worthen. The succeeding 
Six pairs are all about the same size and length, being large, well developed, long, and slender, 
about one-half to two-thirds as thick as the first pair (406°), with no traces of a gill; the second 
pair are a little stouter than the others and apparently spined on the penultimate joint; the sev- 
enth pair the slenderest and nearly as long as the first pair; the three basal joints are long and 
slender, the third very distinct, long, and slender; fourth joint long, slightly swollen in the mid- 
dle; fifth equal to the sixth in length, but slender, slightly thickened towards the distal end; the 
sixth somewhat longer than the fifth, ending in a point; none of the terminal joints appear to be 
chelate. 
The abdominal appendages are distinetly biramous and schizopodal in their appearance. Each 
apparently consists of a small, narrow, jointed limb and a larger exopodital branch (or gill| ; see 
406%»), We can see traces of the first two pairs. In another specimen (501%) the first three pairs 
of abdominal legs are to be plainly seen; the exopodital or respiratory and swimming ramus is 
sessile, lanceolate-oval, and broad, thickened on the hinder (?) edge. In Mr. Carr’s specimen No. 
1 are distinct traces of a biramous append ige on the fourteenth and fifteenth (penultimate) seg- 
ments; and in his No.3 there are to be seen the traces of the second—fourth pairs of abdominal feet 
with doubts rami, the hinder ramus the smaller and narrower. In an abdominal foot (in Lacoe’s 
No. 406) the second joint is narrow, lanceolate-oval, rounded at the tip, from which arise a series 
of long slender sete, about twelve in number, which form an oar-like appendage equaling in size 
the basal joint; total length of the limb 14.5" (the basal joint 8"™, the row of sete 6.5"™"=14,5™™), 
These legs remind us somewhat of those of Squilla, as do the first thoracie pair, from their being 
larger than the others and armed on the under side with stout spines. 
The telson is very long and slender, narrow, acute, the end very slender, with long sete on 
each end; it is a little longer than the caudal feet (aropoda) on each side of it. The caudal feet, 
or sixth pair of uropoda, are divided into two long, large, acute rami (endopodite and exopodite) 
arising from a small, short basal joint (Carr’s No. 1). The two rami are of nearly the same size 
and length, both edges of each branch being setose (the sete are not so numerous and close as 
represented in Meek and Wortheu’s figure). 
Of forty specimens examined, the total length of the largest example, including the eaudal 
appendages, but not including the antennwe, was 75™™ (Lacoe’s No. 55"); another still larger 
(No. y*) was 85™™ in length; a specimen received from Mr. Carr was 55™™ in length. 
In a specimen of A. event, 45™ in length, 1 made the following measurements: Width of 
the body, 6-7" (in Lacoe’s 501”: Width of first cephalic segment, 5.5°"; of second segment, 6"; 
length of first and second head-segments together, 6""; length of rostrum, L""; length of sixth seg- 
ment, 3.5"") ; length of first antennw, about 12"; ie igth of second antenne, 26°"; length of first pair 
of feet, 20°"; greatest width of fifth joint of first feet, 2°"; length of abdominal feet, 18-19"; length 
of telson, 13"°; length of caudal appendages, 12"", 
Many of the specimens are preserved flattened out, showing the back, with the legs spread 
out symmetrically on each side; others are preserved lying on their side, with the body somewhat 
arched, and then they present a shrimp-lke appearance, though on a superficial examination 
reminding one of an Amphipod lying on its side, 
The foregoing remarks apply to the larger specimens described by Meek and Worthen as 
Acanthotelson event. I cannot with certainty point out any distinctions from A. stimpsoni M.& W., 
the first-described species; the smaller specimens, which might be referred to the latter species, 
are evidently the young of A. event M. and W. Hence the specific name should be Stimpsoni. 
The characters of this Crustacean are such as to forbid our referring it to any known group ; 
we therefore suggest that it forms the type of a suborder of thoracostracous Crustacea, which we 
would designate as the Syncarida. 
What we should regard as the differential characters of the group Synearida, to which Acantho- 
